Process for conducting chemical reactions involving corrosive materials



Re n Os E TB la 06. VE T Nn T IIL MA L. E. BUSBY PROCESS FOR CONDUCTINGCHEMICAL REACTIONS INVOLVING CORROSIVE MATERIALS Filed May 7, 1953 Oct.23, 1956 ACID INLET LINE .Il is.

SUPPORT PORCELAIN vEssEL oN BoTToM I-IEAD oF sTEEL vEssEL TANTALU'M sEALTANTALUM SLIP LINE FILTRATE QUENCH INLET LINE United States Patent OPROCESS FOR CONDUCTING CHEMICAL REAC- TIONS INVOLVING CORROSIVEMATERIALS Lyle E. Busby, El Cerrito, Calif., assignor to Standard OilCompany of California, San Francisco, Calif., a corporation of DelawareApplication May 7, 1953, Serial No. 353,599

3 Claims. (Cl. 260-515) This invention relates to a process forconducing chemical reactions which involve the handling of highlycorrosive reaction mixtures at elevated pressures.

There are a number of chemical reactions which involve the employment ofreactants and operating conditions which give rise to extremelycorrosive conditions. ln many instances the corrosivity of the reactionmixture under reaction conditions is so great that none of the materialsavailable for construction of pressure-resistant reaction vesseis has alife expectancy suiiciently long to provide economic justification fortheir use in construction of a reaction vessel. Further, the pressuresrequired in order to carry out the reactions at rates and to degrees ofcompletion necessary in practical commercial operation are so great thatthe possible failure of the reaction vessel as a result of corrosioncreates a safety hazard too great to be accepted. While there are anumber of highly corrosion-resistant materials which have suflicientlylow corrosion rates to enable them to function for long periods of timeunder highly corrosive conditions, these materials lack the structuralstrength necessary to enable them to withstand the reaction pressures.

it has now been found possible to carry out chemical reactions whichinvolve contacting a lluid highly corrosive to ferrous metals with afluid relatively non-corrosive to ferrous metals at high pressures andtemperatures by maintaining a reaction zone bounded by a highlycorrosion-resistant, pressure-unresistant material within and in freeHuid communication with a hydraulic pressure zone bounded by apressure-resistant material, continuously passing the non-corrosive uidat an elevated pressure into the hydraulic pressure zone and through thehydraulic pressure zone into the reaction zone, continuously passing thecorrosive fluid at an elevated pressure from a point outside thehydraulic pressure zone directly into the reaction zone and continuouslyremoving the reaction product mixture directly from the reaction zone toa point outside the hydraulic pressure zone.

The invention may be better understood by reference to the appendeddrawing which is a diagrammatic illustration of an apparatus and processflow suitable for the practice of the invention.

Reaction zone 1 is enclosed or bounded by shell 18 formed from amaterial highly resistant to acid attack, such as porcelain. Thereaction vessel is provided with an inlet 2 and an outlet 3. Thereaction vessel may be a unitary structure or, if it is a large vessel,it is desirably fabricated in sections which are bolted together asindicated at joints 4, employing a nickel alloy having a coefcient ofexpansion approximately equal to that of the porcelain in fastening thesections together. The hydraulic pressure zone 5 is bounded on theinside by the wall of the reaction zone and on the outside by steelshell 6. It may be desired to line or clad the shell 6 with an alloysuch as Type 304 or Type 316 steel to resist attack from the fluidiiowing in the hydraulic pressure zone 5, or to line with an alloy suchas Hastelloy B or Hastelloy C to reduce metal loss which would occur during an operational upset if acid should get into the hydraulic pressurezone. Type 304 and Type 316 steels are American Iron and Steel Institutedesignations for austenitic chromium-nickel steels. The hydraulicpressure zone has an inlet 7 and is in free fluid communication with thereaction zone through reaction zone inlet 2. Acid inlet line 8 isarranged as illustrated to pass the acid from a point outside thehydraulic pressure zone through the hydraulic pressure and into thereaction zone without permitting the acid to contact any part of thehydraulic pressure zone. A tantalum tube 11 is desirably employed toconduct the acid from the exterior of the hydraulic pressure zone intothe reaction zone. Tantalum is highly resistant to corrosion and it isnow feasible to construct small tubes and lines from it. The tantalumliner is desirably held in place by boltng it to a replaceable exterioracid line as shown. The porcelain reaction vessel 1 is supported on thebase of the hydraulic pressure zone by blocks 16 which may be porcelain,steel, or alloy blocks. Provision can be made for stabilizing thereaction vessel within the hydraulic pressure vessel by insertingsupporting blocks in the upper part of the annular space between thewalls of the reaction vessel and the hydraulic pressure vessel. Theupper portion of the hydraulic pressure vessel includes a removable topsection which is fastened to the lower portion of the hydraulic pressurevessel by bolts 10. A tantalum seal 17 is provided as shown to preventthe corrosive reaction mixture leaving the reaction zone through outlet3 from entering the hydraulic pressure zone. The reaction productmixture is withdrawn from the reaction zone through outlet 3 and fromthe outlet assembly illustrated through line 12. The outlet assembly andline 12 are desirably constructed of a highly corrosion-resistant alloysuch as Hastelloy B or Hastelloy C, or lined with tantalum or glass. Theoutlet assembly is replaceable and is fastened to the exterior wall ofthe hydraulic pressure zone by bolts 13, the tantalum slip liner 17being gripped between the wall of the hydraulic pressure zone and thewall of the outlet assembly. A quench line 14 is desirably provided topermit passage of a cold inert liquid into the reaction mixture justbefore its withdrawal in order to reduce the rate of corrosive attackupon the outlet assembly. Quench line 14 is desirably a tantalum tubeheld in place between the outlet assembly and alloy line 15 which isbolted to the outlet assembly and which carries the quench liquid to thepoint where it enters the tantalum tube.

Hydrolysis reactions requiring high temperature and pressure and highacid concentration may be carried out pursuant to the invention withoutdiiculty. The amides of isophthalic acid and terephthalic acid may behydrolyzed to produce the acids. These amides are diicult to hydrolyzeand if the acid product is intended for use in alkyl resins, it isnecessary that the hydrolysis be so complete that the acid product issubstantially completely free of amide nitrogen. To achieve properhydrolysis in a reasonable period of time, it is necessary to employtemperatures from about 300 F. to 550 F., preferably from about 400 to500 F., and pressures ranging from about p. s. i. a. to 1000 p. s. i. a.suicient to maintain the water in liquid phase. Acid concentrationsranging from 2 normal to l5 normal, or higher, exist in the hydrolysisreaction zone during the reaction period. The amide feed to thehydrolysis reaction ordinarily contains ammonium phthalates in additionto the phthalic acid amides.

Pursuant to the invention, the amide feed and water are passed throughinlet 7 into the hydraulic pressure zone 5 at a temperature of 400 to500 F. The aqueous amide feed fills the annular space which constituteshydraulic pressure zone 5 and flows through inlet 2 into l the reactionzone. Sulfuric acid ordinarily at a concentration of 50 to 100% ispassed directly into the reaction zone through line 8 and tube 11. Inthe reaction zone the hydrolysis proceeds at a temperature ranging from40() to 500 F. and ordinarily at a pressure in excess of 500 p. s. i. a.The hydraulic pressure of the amide feed exerted against the exteriorsurface of the reaction zone equalizes the reaction pressure exertedagainst the interior surface of the reaction zone, making it possible tofabricate the reaction zone from materials such as porcelain which havea high resistance to corrosion, but lack the structural strength towithstand the reaction pressure. The reaction vessel is ordinarilyoperated full of liquid and mixing may be obtained by providing asuitable mixing nozzle for acid injection.

The hot reaction product is withdrawn from the reaetion vessel throughoutlet 3 and through line l2 of the outlet assembly. The reactionproduct is cooled to precipitate phthalic acids and filtered. Thefiltrate is cooled and returned through line and tube i4 to quence thereaction product to a temperature below about 300 F. prior to itswithdrawal.

A mixture of meta-xylene and para-xylene containing 85% meta-xylene and15% para-xylene was oxidized by heating it with water, sulfur andammonia to a temperature of about 630 F. under a pressure sufficient tomaintain the water in liquid phase. The xylenes were oxidized tophthalic acids which existed in the reaction product as phthalic acidamides and amm-onium phthalates. The reaction product was cooled,stripped with steam to remove hydrogen sulfide and ammonia, treated withactivated charcoal, and filtered to remove the charcoal, color bodiesand elemental sulfur. The treated reaction product had a calculatedphthalic acid content of 8% by weight, the phthalic acids being presentin the form of amides and ammonium salts. The nitrogen content of themixture of phthalic acid derivatives was 7.5% by weight. Approximately60% of the phthalic acids was in the form of ammonium salts andapproximately was in the form of amides. Hydrolysis of this reactionproduct is accomplished pursuant to the invention by preheating thereaction product to 480 F., passing it into the hydraulic pressure zone5 shown in the drawing through line 7 and thence through inlet 2 intoreaction zone i. Sulfuric acid at a concentration of 93% by weight isintroduced into the reaction zone through line 8 and tube 11 at a ratesuch that 2.3 moles of sulfuric acid to each mole of calculated phthalicacid contained in the salt-amide feed enter the reaction zone. Theternperature of the mixture of sulfuric acid and feed in the reactionzone is approximately 500 F., heat being generated when the acid andfeed are mixed, and the pressure in the reaction zone is approximately700 p. s. i. g. The hydrolysis product is quenched and then withdrawnfrom the reaction zone through outlet 3 and line 12 at a rate such thatthe average residence time of the feed in the reaction zone is 5minutes. The reaction product mixture is cooled to precipitate phthalicacids and filtered to recover phthalic acids as the filter cake. T henitrogen content of the hydrolysis product is below 0.03% by weight andphthalic acids having this low nitrogen content are entirely suitablefor use in the manufacture of alkyd resins.

The hydrolysis may be conducted at somewhat lower temperatures and asatisfactorily low nitrogen content in the phthalic acid product isachieved if the residence time of the hydrolysis feed in the reactionzone is increased. At 450 F. a residence time of 12 minutes is requiredto reach a product nitrogen content of 0.03% by weight.

The reaction vessel can be fabricated from chemical porcelain andchemical stoneware. These terms are well understood by those skilled inthe art and are well described in Engineering Materials Manual, Reinhold1951, at page226 et seq. The reaction vessel can also be fabj @@Carbonorgraphitesbutif these materials are vsl mus be insulatedf ro the F. andat an elevated pressure sufiicient to maintain the steel hydraulicpressure vessel to prevent electrochemical corrosion of the latter. Thereaction vessel can also be fabricated from thin sheets of metals suchas gold, platinum, tantalum, and the like, which are highlycorrosionresistant, but which it is not feasible to make thick enough orstrong enough to, withstand the reaction pressures. The term pressureunresistant material employed in the appended claims` connotes materialsof low tensile strength which would be unable to serve as cont ers foruids exerting great pressures against the interior surfaces.

The polymerization of normally gaseous oletins catalyzed by liquidphosphoric acid has been found extremely attractive on a laboratoryscale, but the high corrosion rates experienced with phosphoric acid atthe reaction conditions have prevented commercial application of thisprocess. Propylene can be polymerized by contact with liquid phosphoricacid pursuant to the invention using phosphoric acid at a concentrationof to 115% by weight calculated as ortho-phosphoric acid, temperaturesfrom 250 to 400 F., and pressures from 200 to 600 p. s. i. a. Whenpropylene polymerization is undertaken the reaction vessel as shown inthe drawing is inverted to permit withdrawal of the lighter hydrocarbonproduct from the top of the reaction zone or used in a horizontalposition with internal bafles similar to H2504 alkylation vessels, butnot steel. The space between acid inlet tube 11 and reactor inlet 2 isadjusted to achieve mixing by turbulent contact of the acid and theolefin feed.

I claim:

1. A process for conducting a chemical reaction involving contacting auid highly corrosive to ferrous metals with a liuid relativelynon-corrosive to ferrous metals at high pressure, which comprisesmaintaining a reaction zone bounded by a ceramic imperforate wall infree tinid communication with a hydraulic pressure space boundedinternally by the aforementioned wall and externally by apressure-resistant wall of lower corrosion resistance, continuouslypassing the non-corrosive fluid at an elevated pressure into thehydraulic pressure space and through the hydraulic pressure space intothe reaction zone, continuously passing the corrosive fluid at anelevated pressure from a point outside the hydraulic pressure zonedirectly into the reaction zone and continuously removing the reactionproduct mixture directly from the reaction zone to a point outside thehydraulic pressure zone.

2. A process for conducting hydrolysis reactions involving contacting astrong mineral acid with an aqueous dispersion of a relativelynon-corrosive hydrolyzable compound at high pressures, which comprisesmaintaining a reaction zone bounded by a ceramic imperforate wall infree fluid communication with a hydraulic pressure space boundedinternally by the aforementioned wail and externally by a pressureresistant wall of lower corrosion resistance, continuously passing saidaqueous dispersion at a temperature above 250 F. and at a pressuresufficient to maintain the water in liquid phase into the hydraulicpressure space and through the hydraulic pressure space into thereaction zone, continuously passing the acid at an elevated pressurefrom a point outside the hydraulic pressure space directly into thereaction zone and continuously removing the hydrolysis product directlyfrom the reaction zone to a point outside the hydraulic pressure space.

3. A process for hydrolyzing amides of isophthalic acid and terephthalicacid by contacting them with a strong mineral acid, which comprisesmaintaining a hydrolysis zone bounded by a ceramic imperforate wall infree fluid communication with a hydraulic pressure space boundedinternally by the aforementioned wall and externally by apressure-resistant wall of lower corrosion resistance, continuouslypassing an aqueous dispersion of the amide at a temperature in the rangefrom 400 to 550 water in liquid phase into the hydraulic pressure spaceand through the hydraulic pressure space into the reaction zone,continuously passing the acid at an elevated pressure from `a pointoutside the hydraulic pressure space directly into the hydrolysis zone`and continuously removing the hydrolysis product directly from thereaction zone to a point outside the hydraulic pressure space.

References Cited inthe le of this patent UNITED STATES PATENTS

1. A PROCESS FOR CONDUCTING A CHEMICAL REACTION INVOLVING CONTACTING AFLUID HIGHLY CORROSIVE TO FERROUS METALS WITH A FLUID RELATIVELYNON-CORROSIVE TO FERROUS METALS AT HIGH PRESSURE, WHICH COMPRISESMAINTAINING A REACTION ZONE BOUNDED BY A CERAMIC IMPERFORATE WALL INFREE FLUID COMMUNICATION WITH A HYDRAULIC PRESSURE SPACE BOUNDEDINTERNALLY BY THE AFOREMENTIONED WALL AND EXTERNALLY BY APRESSURE-RESISTANT WALL OF LOWER CORROSION RESISTANCE, CONTINUOUSLYPASSING THE NON-CORROSIVE FLUID AT AN ELEVATED PRESSURE INTO THEHYDRAULIC PRESSURE SPACE AND THROUGH THE HYDRAULIC PRESSURE SPACE INTOTHE REACTION ZONE, CONTINUOUSLY PASSING THE CORROSIVE FLUID AT ANELEVATED PRESSURE FROM A POINT OUTSIDE THE HYDRAULIC PRESSUREZONE-DIRECTLY INTO THE REACTION ZONE AND CONTINUOUSLY REMOVING THEREACTION PRODUCT MIXTURE DIRECTLY FROM THE REACTION ZONE TO A POINTOUTSIDE THE HYDRAULC PRESSURE ZONE.